National Electrical Code

Code Q&A

Nov. 8, 2004

Q. When is an insulating bushing required on raceway fittings? A. Where raceways containing conductors 4 AWG and larger enter an enclosure, the conductors must be protected from abrasion during and after installation by a fitting that provides a smooth, ...

Mike Holt

Q. When is an insulating bushing required on raceway fittings?

A. Where raceways containing conductors 4 AWG and larger enter an enclosure, the conductors must be protected from abrasion during and after installation by a fitting that provides a smooth, rounded insulating surface, such as an insulating bushing [300.4(F)].

Rigid nonmetallic conduit male-adapter termination fittings are sometimes considered to provide the required smooth rounded insulating surface. But check with the authority having jurisdiction (352.46).

One last thing: insulating bushings aren’t required where a raceway terminates in a threaded raceway entry that provides a smooth, rounded, or flared surface for the conductors. An example would be a meter hub fitting or a Meyer’s hub-type fitting [300.4(F) Ex.].

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About the Author

Mike Holt

Mike Holt is the owner of Mike Holt Enterprises (www.MikeHolt.com), one of the largest electrical publishers in the United States. He earned a master's degree in the Business Administration Program (MBA) from the University of Miami. He earned his reputation as a National Electrical Code (NEC) expert by working his way up through the electrical trade. Formally a construction editor for two different trade publications, Mike started his career as an apprentice electrician and eventually became a master electrician, an electrical inspector, a contractor, and an educator. Mike has taught more than 1,000 classes on 30 different electrical-related subjects — ranging from alarm installations to exam preparation and voltage drop calculations. He continues to produce seminars, videos, books, and online training for the trade as well as contribute monthly Code content to EC&M magazine.